1. Field of the Invention
The present invention relates to a housing for accommodating an electric double-layer capacitor therein.
2. Description of the Related Art
Generally, a boundary across which two different phases of a solid and a liquid contact each other is associated with an electric double layer which comprises positive and negative electric charges that confront each other across a very small distance therebetween. When an electric field is applied between a pair of polarized electrodes, each made of a solid, which confront each other across a separator that is impregnated with an electrolytic solution, the assembly can be used as an electric double-layer capacitor.
FIG. 12 of the accompanying drawings shows a known electric double-layer capacitor housing 61 comprising a bottomed outer case 64 is in the form of a hollow quadrangular prism which accommodates an electric double-layer capacitor 62 composed of a plurality of polarized electrodes having current collectors and stacked together with a separator impregnated with an electrolytic solution and interposed between the polarized electrodes. The electric double-layer capacitor 62 is clamped by a protective strap 63 serving as an insulating member. The electric double-layer capacitor housing 61 also has a lid 65 closing an open end of the bottomed outer case 64, and electrode terminals 67 mounted on the lid 65 and connected respectively to current collecting leads 66a, 66b extending from the current collectors and grouped into respective polarities. To prevent the electrolytic solution impregnated in the separator from leaking out of the bottomed outer case 64, as shown in FIG. 13 of the accompanying drawings, each of the electrode terminals 67 is inserted in a through hole 68 defined in the lid 65, and an insulative sealing member 69 made of an elastomeric material such as fluoroplastics is interposed between the electrode terminal 67 and an inner circumferential surface of the through hole 68. The electrode terminal 67 is crimped over the lid 65 fully around the inner circumferential surface of the through hole 68.
Each of the electrode terminals 67 has an internally threaded surface 70 for electric connection to an external circuit and a tubular member 71 extending upwardly from the internally threaded surface 70. The tubular member 71 is deformed radially outwardly as indicated by the arrows into a bent flange 72, which forces an upper portion of the insulative sealing member 69 to extend horizontally along the lid 65. The insulative sealing member 69 is held against the inner circumferential surface of the through hole 68 and upper and lower surfaces of the lid 65 so as to be uniform in thickness. The upper portion of the insulative sealing member 69 is plastically deformed flatwise as it is sandwiched between the bent flange 72 and the outer surface of the lid 65.
However, the above conventional electric double-layer capacitor housing 61 is disadvantageous in that the ability of the insulative sealing member 69 to seal the interior of the electric double-layer capacitor housing 61 deteriorates with time.